Directing the structures and collective electronic properties of organic conductors:: The interplay of π-overlap interactions and hydrogen bonds

The ethylenedithiotetrathiafulvalene (EDT-TTF) directly functionalized with a primary amido group, which is both a hydrogen bond donor and acceptor group, is prepared from the corresponding ester. The electron-donating ability of EDT-TTF-CONH2 (1), which is comparable to that of bisethylenedithiotetrathiofulvalene (BEDT-TTF) despite the presence of the electron-withdrawing amidic group, allows the successful electrocrystallization of air-stable cation radical salts. Two completely different salts are obtained with the isosteric AsF6- and ReO4- ions; the former has 6:1 stoichiometry, and the latter has 2:1 stoichiometry. Compound (1)(6)(AsF6) crystallizes in the P (3) over bar space group, and the three crystallographically independent donor molecules are linked to each other through a combination of N-H ... O and C-H ... O hydrogen bonds. This strong trimeric motif organizes around the AsF6- ion located on the (3) over bar axis, exemplifying the templating effect of the octahedral anion on the whole structure. The presence of a uniform spin chain, as identified in the crystal structure, is confirmed by the Bonner-Fischer behavior of the magnetic susceptibility. In the 2:1 ReO4- salt, two crystallographically independent organic slabs are interconnected through N-H ... O(Re) hydrogen bonds, demonstrating the overlooked hydrogen-bond acceptor capability of this anion. The salt exhibits metallic behavior with a weak localization below 200 K. Both structures reveal the occurrence of a strong C-H ... O hydrogen bond involving the aromatic CH group of the EDT-TTF core, which is activated by the neighboring amidic moiety. Together with the NH ... O hydrogen bond, it gives rise to a cyclic motif noted R-2(1)(7) in Etter's graph set analysis.